Osseointegration dynamics of mandibular patient-specific implants: A mechanoregulation-based finite element study.

STATEMENT OF PROBLEM: Achieving strong and durable fixation remains a major challenge in mandibular reconstruction with patient-specific implants (PSIs). Most prior studies have focused on initial mechanical stability, with limited attention to the time-dependent progression of biological fixation at the bone-implant interface.

PURPOSE: The objective of this single-patient study was to investigate the osseointegration dynamics of a mandibular PSI using a mechanoregulation-based finite element model (FEM) to explore how the predicted biological fixation behavior relates to the specific design and screw configuration. It was hypothesized that the model predictions for the spatiotemporal pattern of osseointegration would be in good agreement with postoperative quantitative computed tomography (QCT)-derived periprosthetic bone mineral density (BMD).

MATERIAL AND

METHODS

A partial-mandible PSI with an extended fixation wing was designed, fabricated, and implanted in a 19-year-old patient after hemimandibulectomy. A voxel-based FEM was combined with a mechanoregulation algorithm to simulate interfacial tissue maturation over ten 4-week time steps using local micromotion and gap as mechanical stimuli to update a maturity level index (MLI). The final step MLI distribution was compared with 1-year postoperative periprosthetic BMD from QCT, including an element-wise Spearman correlation analysis (α=.05).

RESULTS

Osseointegration started at the distal portion of the fixation wing and progressed proximally, covering about 30% of the wing area by 24 weeks and over 80% by approximately 36 weeks. The 40-week pattern was consistent with the 1-year QCT-derived BMD distribution, showing a moderate positive correlation (Spearman ρ=0.61, P=.004).

CONCLUSIONS

Simulation of the osseointegration dynamics suggested a distal-to-proximal osseointegration pattern and delayed maturation near the osteotomy edge in the treatment under study. It also indicated that achieving a mechanically competent lamellar interface required longer than the idealized 16-week period.